Schematics / RF Circuits
WiFi Can Antenna
Got no dough for a commercial WiFi antenna? Looking for an inexpensive way to increase the range of your wireless network? A tin can waveguide antenna, or Cantenna, may be just the ticket....
RF Spectrum Analyzer
Here's a two part project for an RF Spectrum Analyzer from QST Magazine. Even if you don't build the project there's some great information in here regarding RF filters, mixers, oscillators and more. ...
AM/FM/SW Active Antenna
This circuit shows an active antenna that can be used for AM, FM, and shortwave (SW). On the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. This circuit is designed to be used on receivers that use untuned wire antennas, such as inexpensive units and car radios....
TV Transmitter 
This circuit from Poptronix allows you to send video to any television in the house. It's as educational as it is practical. Since it's from Poptronix, a circuit board layout is included....
4.5-10Mhz Superheterodyne RCVR
With this circuit and a ten foot antenna, you can build a radio that will pick up stations from around the world...
Economy Radar Detector
This circuit uses a 1458 dual op-amp to form a radar detector. C1 is the detector of the radar signal. The first op-amp forms a current-to-voltage converter and the second op-amp buffers the output to drive the piezo transducer....
Simple Superhet Receiver
This idea presents a simple circuit for a superhet radio receiver that can be built up in sections, with each section tested before assembly. The receiver circuitry as presented here can be built for less than $50....